Incentive Plans (Additional Information about Stock Options Outstanding) (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding	5,757,435
Options Outstanding, Avg. Life Remaining in Years	3 years 2 months 12 days
Options Outstanding, Aggregate Intrinsic Value | $	$ 11,354,000
Options Exercisable	3,830,535
Options Exercisable, Avg. Life Remaining in Years	2 years
Range of Exercise Prices per Option $17.57 to $39.02 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit | $ / shares	$ 17.57
Range of exercise prices, upper limit | $ / shares	$ 39.02
Options Outstanding	892,350
Options Outstanding, Avg. Life Remaining in Years	5 years 10 months 24 days
Options Outstanding, Aggregate Intrinsic Value | $	$ 11,354,000
Options Exercisable	55,350
Options Exercisable, Avg. Life Remaining in Years	2 years 6 months
Range of Exercise Prices per Option $45.48 to $51.63 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit | $ / shares	$ 45.48
Range of exercise prices, upper limit | $ / shares	$ 51.63
Options Outstanding	2,379,926
Options Outstanding, Avg. Life Remaining in Years	2 years 9 months 18 days
Options Exercisable	1,556,926
Options Exercisable, Avg. Life Remaining in Years	1 year 7 months 6 days
Range of Exercise Prices per Option $54.21 to $62.98 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit | $ / shares	$ 54.21
Range of exercise prices, upper limit | $ / shares	$ 62.98
Options Outstanding	2,485,159
Options Outstanding, Avg. Life Remaining in Years	2 years 7 months 6 days
Options Exercisable	2,218,259
Options Exercisable, Avg. Life Remaining in Years	2 years 4 months 24 days